Fine MnFe2O4 nanoparticles for potential environmental applications

Abstract

Manganese ferrite nanopowder was prepared by the thermal decomposition of gels obtained from manganese, iron nitrates, and polyvinyl alcohol. The evolution of the gels during the thermal treatment was studied by means of thermal analysis and FT-IR spectrometry. X-ray diffractometry evidenced that manganese ferrite can be obtained as single crystalline phase at temperatures lower than 500 °C. Starting with 500 °C, a secondary phase containing Mn(III) appears, while the annealing at 700 and 1,000 °C leads to Mn0.176Fe1.824O3 and (Fe0.42Mn0.58)2O3, where Mn is at oxidation state (III). The decomposition of manganese ferrite was evidenced also by TG/DSC combined technique of the powder obtained at 400 °C, containing MnFe2O4 as single crystalline phase. Scanning electron microscopy images evidenced the formation of very fine spherical particles (d < 15 nm) of manganese ferrite, in case of the sample annealed at 400 °C. This powder showed good catalytic activity for the oxidative degradation of phenol, in the presence of peroxydisulfate as oxidant agent, so it might be considered a promising nanomaterial for environmental applications.